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Crocanthemum nashii (Britt.) Barnh.
Florida Scrub Sunrose
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G3G4
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 2
Habitat Summary for element in Georgia: sand dunes
Florida Scrub Sun-rose is a perennial, often patch-forming herb with erect or leaning stems 8-16 inches (20-41 cm) tall, covered with branched, white hairs; it is often described as a “sub-shrub” – the base of the stem may be slightly woody. Leaves are found mostly on the stem, only rarely in basal rosettes; they are 6-15 inches long and less than 0.3 inch wide (15–38 × 3–8.4 mm), alternate, linear to narrowly elliptical with pointed tips and tapering bases; the margins are entire; both leaf surfaces are densely covered with branched, white hairs, giving the leaves a gray-green appearance; the leaf stalk is very short (1-3 mm long). The flowers are held in leafy clusters, each flower about 0.6 inch wide (1.2-2 cm), with 5 bright yellow petals and a whorl of many orange-tipped stamens lying flat against the petals and surrounding a white, hairy pistil. Fruits are small (3-4 mm long), hairy capsules with 3 segments. Small, closed flowers without petals develop 1-3 months after the showy yellow flowers do; they are self-pollinating, “back-up” flowers that produce seeds if the showy flowers aren’t pollinated. Both the closed flowers and the fruits are enclosed by hairy, red-tinged sepals and look very similar.
There are four other species of Sun-rose in Georgia’s Coastal Plain: Canada Sun-rose (Crocanthemum canadense), Carolina Sun-rose (Crocanthemum carolinianum), Pine-barren Sun-rose (Crocanthemum corymbosum), and Rosemary Sun-rose (Crocanthemum rosmarinifolium). All occur in dry, sandy woodlands and openings. Florida Scrub Sun-rose is distinguished by a combination of these characters: few or no basal leaves, thick coating of branched hairs on both leaf surfaces, hairy ovaries and capsules, and 3-segmented capsules. NOTE: All North American species of Crocanthemum belonged until recently in the genus Helianthemum and may still be found under that name in older manuals and field guides.
Piriqueta (Piriqueta caroliniana) is very similar to, and occurs in the same habitats as, Florida Scrub Sun-rose. Its flowers have only 5 stamens, and its leaves have toothed margins.
Hoary Frostweed (Crocanthemum bicknellii) occurs in dry, open woodlands in Georgia’s Blue Ridge.
Florida Scrub Sun-rose occurs in southeast Georgia on sand dunes on the east side of rivers with Myrtle Oak and Chapman's Oak.
All species of Crocanthemum have two types of flowers: open, showy flowers that attract pollinators (called chasmogamous flowers) and small, closed flowers that self-pollinate (cleistogamous flowers). The small, closed flowers develop 1-3 months after the showy yellow flowers and produce smaller fruits with fewer seeds than those produced by cross-pollination. The showy flowers are pollinated by a variety of insects, including bees and butterflies. Each showy flower only lasts one day.
Little is known about the ecology of Florida Scrub Sun-rose, but the following information about Carolina Sun-rose (Crocanthemum carolinianum, synonym Helianthemum carolinianum) probably applies: "Carolina rockrose ... has developed a unique survival strategy that involves fire tolerance. The seeds are sown in the soil during the growing season, but they don't germinate in the next season. Since the hard seed coat is impermeable to water, the seeds remain soil-dormant for a long period of time. Together with their small seed size, seed-dormancy allows populations of Carolina rockrose to establish a large seed bank. After a fire has moved through an area, the seed coat softens or cracks due to the heat of the fire, and the surviving seeds germinate shortly after. This mechanism allows ... members of the Cistaceae family to produce a large number of young plants simultaneously and at the right time, thus helping it obtain an important advantage over other plants in the process of repopulating the area. The lack of modern wildfires is probably one reason why Carolina rockrose is not seen in great abundance these days in the southeastern United States." U.S. Forest Service, Plant of the Week (https://www.fs.fed.us/wildflowers/plant-of-the-week/helianthemum_carolinianum.shtml)
Surveys are best conducted during flowering (May–June) when the plants are most conspicuous, but the hairy, three-segmented capsules are distinctive until October. Two important traits, leaves largely confined to the stems and leaves coated with stellate hairs on both surfaces, are also distinctive until later in the year. Further surveys of sand dunes along Georgia’s Coastal Plain rivers are recommended.
Florida Scrub Sun-rose is nearly endemic to Florida, where it is common in scrub habitats, and is known outside of Florida at only one site in Georgia and one site in North Carolina.
Riverine sand dunes and sand ridges in Georgia have been mined and also converted to Sand Pine plantations and residential and commerical developments. They are degraded by fire suppression, pine straw raking, and off-road vehicle use.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Agriculture & Aquaculture | Residential & commercial development | Climate change & severe weather |
| Specific Threat | None | None | None |
Crocanthemum nashii is ranked S1 by the Georgia Department of Natural Resources, indicating that it is critically imperiled in the state. Only one population is known in Georgia. It occurs on private timber land.
All species of Crocanthemum are fire-tolerant, readily re-sprouting from the woody stem base. Riverine sand dunes should be burned occasionally, every 5 – 10 years. Re-introduction of native grasses may be necessary to create the necessary fuel load before fires can be prescribed. Where hardwood tree encroachment is severe, their removal by mechanical or chemical means may be needed. Conduct plant surveys of river dunes and sandhills.
Edwards, L., J. Ambrose, L.K. Kirkman. 2013. The natural communities of Georgia. University of Georgia Press, Athens.
GADNR. 2019. Element occurrence record for Crocanthemum nashii. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, GA.
Moore, D. [n.d.] Plant of the Week: Carolina Rockrose (Helianthemum carolinianum (Walter) Michx.). U.S. Forest Service. https://www.fs.fed.us/wildflowers/plant-of-the-week/helianthemum_carolinianum.shtml
Sorrie, B.A. 2015. Crocanthemum nashii species account. Flora of North America, Vol 6. Oxford University Press. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250101252
Weakley, A.S. 2015. Flora of the Southern and Mid-Atlantic States. North Carolina Botanical Garden, University of North Carolina, Chapel Hill.
Linda G. Chafin
Linda G. Chafin, May 2019: Original account
